Vehicle



Sept. 3, `1946. y Rv. E. cHoATE ETAL 2,406,944

A VEHICLE @riginal Filedsepi. 21. 1940 9 sheeis-sneei 1 Sept. 3, .19.46.

R. E. cHoATE ErAL VEHICLE 1940 9 SheebS-Sheeil 2 Original Filed Sept.21,

gmc/www5 Sept 3, 1946. R. E. CHOATE T Al. 2,406,944

` VEHICLE original Filed sept. 21, 1940 9 sheets-sheet s Sept. 3, 1946.R. E. cHoATE E'rAL 2,405,944

VEHICLE Original Filed Sept, 2l, 1940 9 Sheets-Sheet 4 Sept. 3, 1946. R.E. CHOATE ET .M v

' VEHICLE Original Filed Sept. 2l. 1940 9 Sheets-Sheet 5 SQ m5 NS QQ Imnl M-Hlul SePtl- 3, 1946- R. E. cHoATE ET Al. 2,406,944

VEHICLE Original Filed Sept. 2l, 1940 9 Sheets-Sheet 6 E. cHoATE ETAL2,406,944

VEHICLE Original Filed Sept. 21, 1940 9 Sheets-Sheet '7 Fim-5-a- Sept.3, "1946.v R. cHoA'rE Ei- AL 2,406,944

-V EHICLE Original Filed sept; 21, 1940 9 sheets-)sheet 8 l Sep-t3,1946- R. E. cHoATE ET AL 2,406,944

VEHICLE Original Filed Sept. 2l. 1940 9 Sheets-Sheet 9 plant.

Patented Sept. 3 1946 Y VEHICLE i R03/ E. ohoateana Ellsworth W. Austin,cedar Rapids, Iowa,

assgnors to LaPlant-Choate l Manufacturing Company, Incorporated, CedarRapids, Iowa; a. corporation of Delaware Crignal application September21, 1940, Serial f No. 357,672, now Patent No. 2,347,882, dated May 2,1944. Divided and this application Septomber 13, 1943, Serial No;502,114

12 Claims.

Our invention relates to a vehicle particularly adapted for excavating,transporting; discharging and leveling earth orz comparablematerial,this application being a division of our applicationSerial No. 357,672,iiled` SeptemberrZl, 1940,;

for an Excavator which issued as Patent No. 2,347,882.

`At the present time it is customary in `most commercial operations toprovide the excavating "machine with a separate' tractor, usuallyof the',track-laying type,` arranged at the front of the excavator, to draw theexcavating machine over the ground during most ofthe operation.Sometimes, especially during actual digging, if power is scant, anadditional tractor is brought `up be hind the excavator and acts as atemporary pusher or booster. This arrangement is feasible where extraoperators and equipment are avallable and where there is a good deal ofroom for maneuvering. There is no satisfactory -revers- A' ing actionavailable, however, and even ifV the tractor is operated in the veryslow speed reverse, steering is diflicult partly because of the type ofdraft hitch employed. In ,long haul operations, this is of littleimportance, but in?" short haul operations, the time spent turningaround at the end of the digging trip and at the end of the return tripmay amount to ten or' twenty per cent of the total time. ,An excavatorwhich can be operated and accurately steered`` at high speed in reverseis obviously advantageous in this type of work.

The power requirements of a vehicle ofthis type are very severe. Onrelatively long hauls a representative size of excavator will carryabout? (Cl. ISO-51) of different gear ratios are advisable, but changesfrom one ratio to another should be made `almost instantly to avoid lossofmomentum.l Hence an automatic transmission is highly desirable. y

One of the objects ofour invention is the provisionfof an improvedvehicle particularly adapted for use as an excavator: Y i

Another object of our invention is the provision of a vehicle providedwith its owrrbooster` power- Still another provision. of a vehicleinwhich `the ypower-plant .is arrangedsothat the `weight ofthe-powerplant Fig. 10 is a schematic dagramof the controls object of` `our pinvention is the is well distributed over the ground-engaging Wheels.` Il Anotherobject of our invention isthe provision of a vehicle in whichthe drive from the power-plant to the Wheels is'generally` positive `yetwhich is sufliciently flexible 1go-permit ready maneuvering.

Another object of our invention is the provision of a vehicle capable ofbeing driven in 'a reverse direction for maneuveringiin crampedquarters.

A further object of our invention is to provide an excavator which islargely automatic operation sothat a single operator can handle largeloads at very high speed.` I 1` Another 4object, of our invention is toprovide an excavator in which the amount of excavation is automaticallyregulated for maximum performance of the vehicle.

The foregoing and other objects are attained in the embodiment of theinvention illustrated in the drawings, in which Fig. 1 is a sideelevation of a vehicle in the form of an excavator embodying the objects`of our invention; V

Fig. 2 is a plan of the excavator shown in Fig. 1;

Fig. 3 is a cross-section the planes of which are indicated by the lines3-3 of Fig. 2;

Fig. 4 is a cross-section the planes of which are indicatedby the line4-4 of Fig. 3; c

Fig. 5 is a cross-section the plane of which is indicated by theA line5,-5 of Fig. 4;

Fig. 6 is a cross-section the plane of which is indicated b y the line6-M6 of F ig, 4; v

Fig. 7 is a plan, portions `of the` enclosing casing being removed, ofthe rear .portion of our excavator; 4 c

Fig. Bis a side elevation of a motor vehiclepreferably for use with `ourexcavator; g

Fig. 9 is a diagrammatic plan of the cable `arrangement of ourexcavator;

of our excavator; and Fig. 11 is a schematic diagram of additionalcontrols of our excavator especially forregulating the amount ofAexcavation.

For the purposes of illustration, our vehicle has been shown in the formof an excavator including a maingframe and main bowl structure, theelements of vwhich are articulated for relative motion abouta transverseaxis and which are provided with means ior'controlling such motion. Eachofthe elements is supported on groundengaging Whee1s,i the rearpair, ofwhich are driven by an associated source of power, and the front pair ofwhich not only are steerable but are driven from their own associatedsource of power. The sources of power are under the control of thevehicle operator and transmit their driving force through hydrauliccouplings and automatically shiftable ratio-changing transmissionsresponsive to the speed of the respective driven wheels. The drive isalso transmitted through. reversing gears under operator control andthrough diierential gears under automatic control responsive to thesteering for locking the differentials. The earth-handling devices, thatis, the main bowl, the pusher and the auxiliary bowl, are power-actuatedby operator-controlled cable- Winches and hydraulic cylinders.

The .excavator structure II is supported upon a pair of rearground-engaging wheels I2 and a pair of front ground-engaging wheels I3-alnd is made up o1 a rear, main bowl section I4 articulated to a front,main frame section i6 for relative rotation about a transversehorizontal axis I'I. Relative rotation about the axis is controlled bydouble acting hydraulic piston and cylinder structures I8 pivotallymounted on the frame I6 and connected through stopped bell-cranksA i8 tothe main bowl section I 4. The various instrumentalities within andassociated withthe main bowl, including the bell-cranks I9, aresubstantially as shown in the above-identiedAustin application. Theseinstrumentalities generally com-v prise an earth discharge or pushermember 2I which is translatable within the main bowl I4 and which isconnected by an articulation 22 to an earth-retaining member 23 orauxiliary bowl or front apron which in turn is connected to the mainbowl through a pair of links 24, so that upon forward movement of thepusher 2i the front apron 23 rises, while upon return or rearwardtranslation of the pusher 2I the front apron 23 closes.

While the front apron is open, material is either discharged from orloaded into the main bowl over a cutting yedge 26 .disposed.approximately midway of the length of the main bowl structure'. Uponappropriate operation .of the hydraulic cylinders I8, the cutting edge25 can be raised to its carrying position as shown in Fig. 1, or can belowered therefrom to a maximum cutting position below the surface of theground, such movement being accompanied by relative rotation .of themain bowl section I4 with respect to the main frame section I6 about thetransverse axis I'I and also about the rotational axes of the rearwheels I2 and the front wheels I3. When the .hydraulic cylinders I8 arenotl actuated, but `the liquid is blocked therein, they function asrestraining or locking means to prevent unwanted or erratic relativerotation of the main bowl and main frame members, thereby preserving theselected position of the various parts under the control of theoperator.

The forward portion of the main `frame 4Iii is connected to and includesa steering member 3l which is mounted for .relative .rotation -with re-`spect `to the main frame vabout a vertical 'axis 32, and since the frontwheels I3 are .connected to the steering member there is thus provided ameans for effectuating steering movement of the entire vehicle, theextent ofv steering motionof. .the front `wheels being a rotation. of:substantially 90 degrees in either ldirection from 'the straight-aheadposition, :so `that Ithe vehicle :can be steered with its front wheelstraveling 'in a direction at Aright angles to :the direction v.of therear wheels. This permits very abrupt turning and sharp maneuvering ofthe vehicle in cramped quarters. The steering member 3I is primarily ahollow casing having (Fig. 5) a king pin 34 therein also mounted Withina central mast 33 forming part of the main frame. The king pin 34 isextended to form a pvot connection with a knuckle frame 36 preferablyintegral with the steering member 3I.

In order to e'ectuate relative steering rotation between the main framemast 33 and the steering member 3I, there is mounted on the casing 3|within a steering compartment 3l a bevel ring gear 38 with which meshes(Fig. 6) a 'steering bevel 39 journaled on a collar 4I and also meshingwith bevel ring gear 42 within the compartment and fast on the mast 33.An extension 43 of the collar 4I forms a pivotal mounting for a pistonrod 44 of a hydraulic steering structure (Fig. 4). A double-actingsteering cylinder 41 is at one end mounted on a pvot pin 49 fast withrespect to the steering member 3! and disposed on .an extended bracket5I materially spaced from the king pin 32.

Upon appropriate control of oil ow to and from the chambers ofthecylinder 41, the piston rod 44 is advanced or retracted to rotate theextension 43 and to move the bevel 39, so that relative rotation takesplace between .the ring gears 38 and 42, thus producing relativerotation between the steering member 3l and the mast33 of the mainframe. The gear reduction employed is at a ratio of ,two to one, sothat, for degrees angular motion of the extension 43, degrees angularmotion of the `steering member with respect to the steering mast3l isprovided. Also by use 0f this mechanism, and because of the resistanceto flow of the hydraulic fluid utilized, the steering member 3 I,despite extraneous shocks, remains substantially in the selectedposition, although the operator can, if desired, permit some seepage orleakage in order that a dashpot effect may be provided.

Steering movement is imparted from the steering member 3I to the frontground-engaging wheels I3, through supporting structures which connectthe front wheels to the `rest of .the vehicle. These supportingstructures are substantially identical on opposite sides of the center,and hence a description of one applies to both. Mounted upon thesteering member v3l are parallel rods 56 serving as pivotal mountingsfor a pair of support levers 51 and 58 fulcrumed on the steering memberat their inner ends and at their outer ends connected by parallel pivots59 and 6I to the. enlarged plate end 62 of an axle tube 63. On lthe axletube are disposed bearings 64 and 65 rotatably supporting a wheel 66provided with detachable connectors 61 securing it to a rim 68 on which.a ground-engaging pneumatic tire 69 is mounted.

By this arrangement not only does the tire, rim and wheel unit revolveupon the axle tube 63, but likewise the wheel assembly rises and fallswith respect to the steering member 3| as permitted by the rising andfalling movement of the levers 51 and 58. Thus, rotational movement ofthe steering member about the central vertical axis 32 is accompanied bya corresponding movement of the wheels in unison therewith, toaccomplish steering of the excavator while rising and falling movementof the wheels 'to accommodate for irregularities in the ground ispermitted. This accommodation is resiliently restrained. Interposedbetween pads on the steering member 3| and pads onthe plate 62 is alpairof coil springs 1| for transmitting the weight of the vehicle to theground-engaging wheels. Another pair of springs is symmetricallyarranged, and with this suspension arrangement the steering axis 32 mayremain substantially in a vertical position while either of the frontgroundf engaging wheels can accommodate itself to irregularities in theterrain independently of similar accommodating movements `by the otherwheel. Y

In order to provide a support for the operato-rs station and forpropulsion mechanism, the steering knuckle frame 36, approximatelymidway of its height, is extended to provide a substantially horizontalbeam platform 16 which forms the floor of an operators cab 11 containing^a seat 18 for the operator and a steering wheel 19, together with othercontrol instrumentalities, and from which the operator can see not onlyahead but also behind into the earth-excavating structure, for fullvisual observation of the entire operation.

Situated beneath and partially supported by the floor beam 16 is yasource of power, such as an internal combustion engine 0|. Thispowerplant is peculiar or individual ,to the front groundengaging wheelswhich are driven thereby, and furnishes substantially half of the totalpower supplied to the vehicle. The engine is preferably water-cooled,with the radiator structure 82 forming a linkto assist in supporting theengine, and derives fuel from a tank 83 disposed beneath the driversseat 16. The engine 8| not only supplies power directly to the vehiclebut also has a power take-off housing B4 from which a shaft 86 projectsto drive an air-pump 81 to supply compressed air for operating variousinstrumentalities and likewise to drive a hydraulic or oil pump 88 foroperating other instrumentalities. n

The engine itself terminates in a standard bell housing 89 in which theengine crank-shaft 9| is journaled and which bolts to a housing 93 for ahydraulic coupling. This comprises a toroidal drive member 94 operatingon and with the crankshaft 9| and driving, by hydraulic connection, atoroidal driven member 96 mounted on a driven shaft 91 extending to Vareversing mechanism,

generally designated 98, contained within a hous-, ing 99. This housingis preferably bolted to the cannot be performed by present excavatingstructures. For that reason, the reversing mechanism takes the form of adriving disc |0| which has a middle, neutral position, as shown in Fig.5, and may be shifted by a shifting fork |02 in either direction out ofthe neutral position, either forwardly into frictional engagement with adriven member |03 or rearwardly into frictional engagement with a seconddriven member |04. While the driving and driven members engagefrictionally, it is not intended vthat they act primarily as slippingclutches, but rather the interengagement between the driving member |0|and either of the driven discs |03 and |04 is relatively abrupt, anylarge difference in speed being gradually absorbed by the hydrauliccoupling 93.

. 6 The driven member |03. is connected directly to a transmission shaft|06 which extends through the steering housing 3| and which carries abevel side gear |01. The driven member |04', however, is connected to abevel side gear |08. Together these are freely rotatable with 'f respectto the shaft |06, yet the gear |03 is connected with the bevel gear |01'through pinion gears |09 Arestrained against planetary rotation andmounted in journals within the housing 3|. With this arrangement, whenthe disc |0| is in neutral position, no power is transmitted from thedriven shaft 91 to the shaft |06. When the disc IDI is in frictionalengagement with the disc |03, power is transmitted directly to the shaft|06 and turns it in the same direction as the engine crank-shaft 9|rotates. When, however, the disc |0| is in contact with the disc |04,this latter disc then rotates in the same direction as the enginecrank-shaft, but this direction of rotation is reversed through thepinion gears |09, so that the gear |01 and the shaft |06 are thenrotated in a direction opposite to the direction of `rotation of thecrankshaft 0|. There is, however, no speed changeby means of thisreverse gear transmission, so that there is provided either a completeneutral disconnection or full power transmission in either of twoopposite directions. This is all under the control of the shifting fork|02 which is itself controlled by the vehicle operator.

In addition to the reversing mechanism, 4we provide a ratio-changingmechanism between the source of power and the ground-engaging wheels,and this preferably takesthe form of a spury gear transmission locatedin a casing I I| bolted on `the rear of the steering member 3| and alsoforming asupport for the bracket 5| previously described. Any suitableratio-changing mechanism can be utilized, and any desired number ofratios can be afforded, but for example herein we have disclosed anarrangement which is under the control of the operator or which isautomatically actuated and provides a choice of any one of eight speedsor ratios. This, in conjunction with the reversing mechanism, affordseight speeds rearwardly and eight speeds forwardly between the engineand the ground-engaging wheels. j

In the ratio-changing transmission the transmission shaft |06 carries adriving dog clutch ||2 under the control of a shifting fork I I3 andmovable from a neutral position into either of two extreme positions inengagement either with a gear 4 or with a gear IIE. Each of these gearsisfreely rotatable upon the shaft |06 until it is coupled thereto by thedog clutch ||2 upon operation of the shifting fork I I3. Meshing withthe gears is a pair of cluster gears ||1 and H8,

respectively, which are fast on a countershaft I I9. Also fast on thisshaft is a second shifting dog clutch |2| under the control of ashifting fork |22, so that upon operation of the fork the clutch |2`|couples tothe countershaft H9 either of two gears |23 and |24.

These in `turn mesh with a pair of cluster gears |26 and |21 integralwith a quill |28 revolving around the transmission shaft |06. Fast on`the quill, so far as rotation is concerned, but shiftably slidablethereon, is a Y,dog clutch |29 under the control of a shifting fork 7has two shifted positions with a different gear ratio .effective `ineach, by appropriately shifting these forks a total of eight differentratios is obtainable.

After the speed ratio has been `established in the transmission casingthe drive is taken vfrom the shaft |31 through a pinion |38 meshing witha ring drive gear |39 mounted on a differential spider |4| journaledwithin the steering member 3|. DifferentiaI pinions |42 are carried bythe spider [4| and mesh with side gears |43 and |44. Ordinarily, thedrive from the ring gear |39 is transmitted to the spider and is dividedevenly by the pinions |42 to the two side gears |43 and |44 forappropriate distribution to the ground-engaging wheels. Under certaincircumstances, however, we prefer that the differential mechanism berendered inoperative or be disabled to divide the power, so that in factthe driving wheels are locked together for rotation in unison with thedrive gear |39. This is of particular value when the vehicle isnegotiating very rough terrain with different traction conditions indifferent localized areas thereof, and for that reason we provide adifferential locking mechanism which precludes any power or torquedifferential between the wheels on opposite sides of the vehicle.

Extending from the spider |4| is a friction disc |46 with which can beengaged a friction disc |41 axially movable on but splined to the hub ofthe side gear |43. Axial movement is provided by a shifting collar |48having an interengaging serrated connection |49 with a non-rotatablethrust hub abutting the disc |41. The collar |48 is controlled forpartial rotation by an actuating lever so that normally the actuatinglever |5| is in a position with the serrations |49 nested and the discs|45 and |41 out of engagement. This permits free differentiation. Butwhen the lever |5| is slightly rotated, the serrations |49 arerelatively moved, thereby translating the disc |41 axially intofrictionally locked engagement with the disc |46 so that the side gear|43 is immovably locked to the spider |4| and the entire differentialmechanism therefore revolves as a unit with the driving ring gear |39.

From the side gears |43 and |44 the drive on each side of the centerline is exactly symmetrical, so that a description of one side willsuffice.

rlhe side gear |43, for example, has its hub extending through andjournaled in the wall of the steering member casing 3| to connect with auniversal joint (not shown) enclosed in a ball housing |52 from which asliding joint (not shown) encased in a telescoping housing |53 transmitsthe drive to a second universal joint (not shown) in a ball housing |54.In this fashion the drive is transmitted between the relativelystationary steering member and the vertically movable wheel. From theinterior of the universal joint ball |54 there projects an axle |56journaled within the axle housing tube 63 and extending to a final gearreduction. This final gear reduction is preferably of the planetary typeand is entirely contained within the interior of the wheel housing 96.It includes a sun gear |51 at the end of the axle |56, which meshes witha plurality of star gears |50 journaled on a spider |59 stationary withthe axle housing tube 63 and in turn meshing with a driven ring gear |5|fast on the wheel housing 66 and enclosed by a cover plate |62. By thisarrangement of final drive gears it is possible to have a relativelyhigh- Speed .and smal1 drive axle |56 yet a relatively slow speed of theground-engaging wheels.

We preferably provide means for braking the vehicle, and, as an example,utilize a portion of 5 the wheel housing G9 as a brake drum. Within suchdrum and pivotally mounted on a brake plate |63 splined on the axlehousing tube 66 are brake shoes |54 which are fluid actuated by aninterior cylinder |66 connected by a fluid conduit |61 and passages |08in the axle tube to a connection |59 going to the cperators controlstation in the customary fashion.

Not only is a driving and braking structure employed with the two frontground-engaging wheels |3 from a front engine 0|, but in an entirelysimilar fashion, except for the steering and the articulated, resilientsuspension, there is provided at `the rear of the vehicle an entirelyseparate and independent engine which is disposed in a rearwardextension |11 of the main bowl structure This arrangement behind therear ground-engaging wheels l2 is substantially symmetrical about thecenter of the earth-carrying structure with the engine dispositionrelative t0 the front ground-engaging wheels, so that the weight is atall times uniformly distributed. The engine |18 is entirely comparableto the engine 8| and is similarly provided with a power take-off |84 anda power take-off shaft |86 which connects through universal joints |81and a driveshaft |00 to a winch mechanism |99. This winch structure isoperator-controlled and preferably is provided With a pair ofindependently actuated drums 9| and |92, each of which is normally leftin a braked position but may be freed for unhampered rotation or can beconnected for power driving to the engine |01, all under the control ofthe operator.

As particularly shown in Figure .9, the winch |9| is provided with acable |95 which extends about pulleys |93 on the pusher 2| to ananchorage |94. Thus, when the winch |9| is energized, the pusher 2| isurged forwardly. Similarly, the winch |92 is provided with a cable |91extending around pulleys |98 on the pusher 2| to an anchorage l 99,-sothat when the winch |92 is poweroperated, the influence of the cable |91is to retract or withdraw the pusher 2| toward its rearmost position.

The engine |16 is provided with its own radiator and similarappurtenances and is connected to the rear ground-engaging wheels |2 inexactly the same fashion as the front engine 8| is connected to thefront wheels, but there is no power connection between the two engines.There is, however, within a housing 203 a duplicate of the hydrauliccoupling 94, and within a housing 204 there is a duplicate of thereversing gear IGI. Also, within a transmission housing 205 there is aduplicate of the ratio-changing mechanism contained within the housingThe rear ratio-changing transmission is effective to drive a reardifferential mechanism provided with a locking clutch and identical withthat afforded for the front wheels. The rear differential is disposedwithin a central housing 201 on which the winch structure |89 is mountedand which is included in and connected to the main frame of theexcavator. The rear wheels |2 o are suitably provided with nal gearreductions within the wheel housing 293 and, although they are mountedfor rotation, are not steerable nor independently articulated for risingand falling movement due to road irregularities.

75 Except, therefore, for the steering and suspen- Vin response tovarious selected functions, and,

while the control elements themselves are illustrated in the remainingfigures, they are diagrammatically shown in theirfunctional relationshipih Fig. 10.

Preferably, all of the control instrumentalities are arranged withinconvenient operating distance of the operator stationed within vthe cab11 and are connected as diagrammatically illustrated in Fig. l0. Tocontrol `the power output of the front engine 8| there is provided athrottle or governor controller constituted by an operating handleconnected by linkage 252 to the springi 253 of an engine governor 254.By varying the tension of the spring, the effector the governor 254 onthe'fuel supplier '256 of the engine 8| is varied. Thus, for any givenor set position of the lever 25|, the engine is automatically maintainedby the governor 254 at substantially the established level of output.Similarly, and arranged in very Vclose juxtaposition to the lever 25|,is a controller 251 which is connected by linkage 258 to the speedgovernorl 259 of the vengine |16, the governor being likewise connectedby a rod 268 to the fuel supplier 26| of thatA engine. Since the levers251 and 25| are arranged close together, they either can besimultaneously operated as a unit by the vehicle operator so as toproduce identical= changes in operating characteristics of both engines,or can be individually operated for different power output `from eachengine. A

For usual operation of the vehicle, the control- 1ers 25| and 251 areoperated together and uniformly, so that both engines 8| and |16 producesubstantially equivalent amounts of power and produce substantiallyequal torques at the driving wheels. In this type of operation theengine 3|, in propelling the vehicle forward, produces a torque reactionwhich tends to move the forward portion of the main frame in acounter-clockwise direction (Fig.v 3) about the axis of the front,ground-engaging wheels, whereas the rear engine |16 produces Va drivingtorque reaction which tends to rotate the rear portion of the main frameand main bowl structure also in a counter-clockwise direction (from thesame viewpoint) about Vthe axis of the rear wheels. Thesetorque-reactions, being exactly equal, neutralize each other and do nottend to produce any rotation about the transverse axis |1. Y

Under other types of operation, however, the two engines 8| and |16 areindividually operated by individual manipulation of the levers 25| and251 to produce different torque effects upon the front wheels and therear wheels; and 4since the driving torques are in different amounts,the cor-, responding reactions tendV to induce a relative rotation ofthe main frame and main bowl structure about the transverse axis |1.This is normally resisted by the hydraulic cylinder; mechaoperator, thetorque reactions can be utilized for relatively rotating the parts ofthe structure. The individual controls for the engines are particularlyvaluable in operating the vehicle where very sharp turns are made andespecially where the terrain is exceedingly rugged and contains chuckholes or mud holes, since, by selective application vof the motivepower, advantage may be taken of the most favorable traction. But forall ordinary purposes under reasonably favorable conditions, both of thecontrollers 25| and 251 are operated in strict conjunction.

i For controlling the steering of the vehicle, the Aoperator is providedwith the steering wheel 19 which is connected through a resilient means,such as a spring 262, with a bodily movable follower valve 263. Thisfollower valve controls the flow of hydraulic lluid through conduits 264and 266 to opposite ends of the cylinder 41, so that as the steeringwheel 18 is turned, the follower valve 263 produces an equivalentdisplacement of the cylinder and, correspondingly, an equivalent turningof the ground-engaging wheels. The wheels consequently are turned bypower and are held in positions at all times corresponding to the turnedposition of the steering wheel.

To supply not only the cylinder 41 but likewise the other hydraulicinstrumentalities with a supply of hydraulic uid, the pump 88 has itsintake 261 extending to a tank 268 and discharges through an outletconduit 269. A by-pass check valve 21| regulates the pressure within theoutlet conduit, returning any excess of fluid to the tank 268. Afollower valve pressure pipe212 extends through a flexible connection213, to the follower valve and supplies appropriate chambers within thevalve with pressure fluid. A return flexible conduit 214 is connected toa return pipe 216 extending to the tank 268'. The port arrangementwithin the follower valve is such that as the valve is moved in responseto the 4steering wheel rotation, the pressure fluid is communicatedthrough the valve body 211 to the appropriate portion of the cylinder48, so that for any degree of steering wheel rotation the l front wheelsare steered an equivalent amount through the intervening servo action ofthe follower valve and the hydraulically actuated cylinder.

Since the steering of the vehicle is of the central pivot or fifth wheeltype, it is deemed desirable progressively to limit the amount ofturning angle with increasing speed, so that, while the vehicle is fullymaneuverable when it is operating at low speed and in cramped quarters,the amount of' turning which can be effected at higher speeds isprogressively decreased as the vehicle speed increases. Since theexcavator is intended to haul very heavy loads of earth at a relativelyhigh rate of speed, an automatic means is provided for insuringstability by precluding excessive steering movement; that is, byreducing the range of possible steering as the speed is increased. l

For this reason, there is driven by the rear wheels I2, or is responsiveto the speed thereof,

an excavator speed governor 218 which translatesv a controller219 as thevehicle speed increases. Themovernent of this controller is likewisetransmitted through a similar control rod 28| fastened thereto andYeffective through a link 282 to translate` a restraining block 283against the urgency of areturn spring 284. The block has a cam face 286which is contoured to cooperate with a the cam 28-1.

`pipe 216.

lthe cylinders I8.

l 1 cani- 281 moving simultaneously with an-d fast upon the followervalve 263. When the parts are in the position shown in Fig. 10, which isthe low-speed position, there is no restriction Whatsoever upon thetransverse translatory movement of the cam 291, and full steering may beobtained.

`But as the speed of the vehicle increases, the

governor 218 actuates the control rods 219 and 28| and, through theconnection 232, tensions the spring 294 by translating the block 283toward When that is done, the cam face 286 progressively limits thetranslatory movement of the cam, and when the cam block is fully incon-tact with the cam 281 the translatory movement thereof is limited toa predetermined amount-for example, 30 degrees of steering of the frontwheels each side of center position.

Since the steering wheel 19 is connected to the follower valve 203 bymeans of a resilient connecting spring 262, even if the operator shouldoperate the wheel 19 beyond the permissible 30 degree limit at highspeed, for example, the cam block 283', being actuated by a superiorforce,

will restore the cam 281 and the follower valve 233 toward centralposition sufficiently to bring the steering within the establishedmaximum range at that speed. Thus, while steering is entirely free atrelatively low speeds and is restricted to a predetermined maximumamount at high speeds, the range of restriction gradually varies betweenthe low-speed and highespeed limits as the cam 291 is contacted bysuccessive portions of the cam face 289. This mechanism vprovides anautomatically effective means for ing' wheel 19 is a controller 29|which is effective to rotate a conventionally illustrated hydraulicvalve 292 for controlling the supply of hydraulic fiuid through thesupply pipe 269 to the cylinders I8 connected in parallel, and thedischarge of fluid therefrom through the discharge These are thecylinders which determine the resistance of they mechanism to torquefreactions of the engines when driving and also govern the position ofthe cutting edge 26. By

appropriately operating the controller 29| the operator can admit,release or hold hydraulic fluid within the cylinders I8 to retain theparts While many other control instrumentalities on the excavator .canbe hydraulically actuated, it is preferred, in the present embodiment,to utilize hydraulic actuation only for the steering .and for Theremaining power-operated instrumentalities are preferably operatedthrough the medium of compressed air. Thus, the compressor 81, driven bythe forward engine 8|, sup- 'plies air under a predetermined regulatedpressure to a tank 30|. 'line 302 extends to valves 303 and 304 whichcon- Itrol the brakes on the front wheels and on thev From the. .tank apressure rear Wheels respectively. 'I'he valves 303 and 394 Aareprovided with individual pedals 306 and 301 located side by side andconvenient to the driver in the operators cab, so that the front end ofthe "device may be braked separately from the rear end. The brakingproduces torque reactions f quite similar to those produced by theengine driving forces, except lthat they occur in a reverse directionand, unless exactly equal (in which case they neutralize), are alsoresisted by the doubleacting hydraulic chambers `I8. While ordinarilythel operator controls both of the pedals 306 and 301 in unison, thisbeing facilitated by their location in juxtaposition, the operator can,since the brake pedals are separate, indivi-dually control the brakes tofacilitate maneuvering of the Vehicle.

In accordance with our invention, and in order to assist in theversatility and maneuverability of the vehicle, we provide means forpermitting the differential mechanisms, such as I4I, normally tofunction when the vehicle is turning a substantial amount but to renderthe differentials inoperative or to disable them when the vehicle isgoing in a straight path or approximately so. Further, We preferablyarrange matters so that the front differential mechanism and the reardifferential mechanism are disabled under difierent conditions. For thatreason, the air pressure line 302 has a branch line 308 extending to acontrol valve 309 spring-pressed into inoperative position normally buteffective when operated to establish connection between the branch 308and an air line 3| I extending to an operating chamber 3|'2 connected tothe lever |5I for operating the locking clutch on the frontdifferential. The branch 308 likewise extends to a control valve 3I3normally ineffective but, when actuated, effective to establishcommunication through a line 3I'4 to an operating chamber 3|6 of asimilar character but working upon the locking clutch lever for Athedifferential of the rear engine.

Thus, when the valve 309 is operated, the air pressure is eiective tounlock the front differential, whereas when the valve 3|3 is actuated,the air pressure is effective to unlock the rear differential. Thedifferential locking and unlocking is preferably responsive to steeringmovement. Consequently, moving in conjunction with the steering pistonrod 44 there is a cam block 3| 1 which has a narrow notch 3I`8 on oneface, ineffective when the steering is straight ahead, but effectiveupon a turn of approximately degrees, either side of center, totranslate the valve 309.

CSI

' 45 Thus, While the front ydifferential is locked for all steeringpositions of the front wheels between 5 degrees left of center and 5degrees right of center, as soon as this ,amount of turning is exceeded,the front differential is unlocked and the drive of .the front engine isdistributed to the two front wheels. The. rear differential, however,remains locked until the front steering approaches a Value approximately30 degrees either side of center, as governed by a Wide cam notch 3I9also in the block 3|1, which is effective to displace the controller3|3. For all values of steering, therefore, substantially in excess of30 degrees left or right of straight-ahead position, the reardifferential is unlocked and the rear wheels are fully difierentiated,or the power of the rear engine is then distributed to the twov rearwheels in varying amounts. Upon restoration of the steering mechanismtoward center position, the rear differential is relocked as soon as therange between 30 degrees left of center and 30 degrees right of centeris entered, while as soon as the range between 5 degrees left of centerand 5 degrees right of center is entered, the front differential isrelocked.

70 It is considered desirable to reduce the power voutput of the rearengine when .the front wheels are turned or steered a large amount, sothat 'the driving force of the rear wheels does not tend lto produce askid of the front end. As a coni' 75 vement way of doing this, the airline 3I4 is 13 branched to connect to a controller 3|5'e1lective whenenergized to position a cam 323 in the `path of a cam 325 mounted on thecontrol rod-260 of Vthe rear engine.A When the front `wheels are steeredmore than 30 -degrees either side of center, the controller 3|5progressively reduces the rear engine speed.

Conveniently arranged next to the control lever 29| for raising andlowering the cutting edge, are the winch control levers. For example, acontrol lever` 32| is effective upon a conventional valve 322 to governthe now from a supply pipe 323 to eitherof the oppcmite ends of anactuating charnber 324 which is of a standard type repeatedly utilizedin the structure and normally centralized to a neutral position byequally acting springs 326 and 321. When thevalve 322 is maintained inneutral position by the median position of the lever 32 the winch islikewise in neutral position and transmits no power. However, when thelever 32| is rocked in one direction, air is admitted to one end of thechamber 324, thereby placing the winch in braked position, and when thelever 32| is swung to its opposite extreme position the winch isconnected to power. Thus, the lever 32| is effective to control one ofthe winch drums, for example, drum ESI. A lever 33| con'-A trols astandard valve 332 for regulating the supply and discharge of air t0 andfrom the opposite ends of an actuating chamber 333 which is effective tocontrol operation of the winch drum |96. so that by operation of thegrouped levers 29 ,32| and 33|, the operator can effectuate all oftheusual controlling mo-tions of the earth-carrying and handling structure.

Since the vehicle is designed to be operated as rapidly in a reversedirection as it is in forward direction, to obviate the necessity ofturning around,` the control of the reversing clutch IUI for th'e frontengine and of the corresponding clutch for the rear engine is.simultaneously effectuated. A reversing lever 334 controls a standardvalve 33,6V to provide any one of three positions thereof. In anintermediate, neutral position, air from the main 323 is excluded from afront operating chamber 33'! as well as from a rear operating chamber338. The piston in each of .these chambers is spring-centralized, aspreviously described, when no air pressure isy exerted thereupon. Thechamber 331, for example, is

leffective to hold the shifting fork |32 of the front reversingstructure in neutral position, as shown in Fig. 5. The chamber 338 forthe rear structure is identical in operation. u l

When, therefore, the lever 334 is moved in one direction out of centralposition, air is admitted ,to one end of both of the operating chambers331 and 338, and the shifting forks are effective to Yconnect thestructure for motion in one direction, for example, forwardly. When thecontrol lever 334 is shifted to its opposite extreme position, the airis released from the previously charged end of the operating chambers331 and 338 and pressure air is simultaneously introduced into theopposite ends thereof so that the shift- V ing forks controlled therebyare simultaneously vshifted into opposite extreme positions and areverse coupling or direction of drive is effectu- `ated. Thus, thedirection of advance of the vehicle is under the control of the operatorby a f single lever, although other parts of the drive are quiteseparate.

While the reversing clutches have .a slight slippage at very hightorques, the shift due to the pneumatic controllers 331 and 33B isrelatively coupled with the front wheels.

abrupt,- andV excessive momentary torque is pri-- marilyfabsorbed in thetwo liquid couplings, one for each power plant. Since these liquidcouplings are in part responsive to centrifugal forces, dependent uponthe speed of the respective engines, andsince the engines areindividually controlled through the-controllers 25| and 251, it ispossible, by manually or automatically minimizing-the power output of`one engine, for example, the rear engine during very sharp turns, todrive substantially by the other or front engine alone, so th'at `thedirection of rotation of the rear wheels relative to each other andrelative tothe rear Vengine is not particularly material. That is, oneengine, when operating relatively slowly, is substantially uncoupled bythe hydraulic coupling, so that the remaining mechanism may be operatedin a reverse direction without affecting the one engine.

. Forexample, when the front wheels are turned substantially at 90degrees to the longitudinal direction of the vehicle, the rear enginecan be idle and the front engine can be operated at considerable speedand power output so as to be The front drive can then. bealternatedbetween forward and reverse, to move the forward end of the vehicle inan Varcuate path substantially about the center of the 4rear wheel axisas a turning pivot. `But at this time the rear yengine, although beingreversely Yand forwardly related to its ground-en-` gaging wheels alongwith the front engine, is substantially ineffective upon the rear wheelsbecause its-low speed effectuates a hydraulic uncoupling. Under theseconditions the rear differential is also unlocked. The front end of thevehicle can be operated substantially at right angles and with fullpoweroutput. This is of considerable importance in maneuvering incramped quarters and where the ground conditions are quite irregular.Thus, by reason of the common reverse of the two engines but of theseparate control of the power output of each and th'e automaticuncoupling feature of the hydraulic couplings at low enginespeeds,`there is provided a somewhat interrelated but extremely flexibleand maneuverable power transmission system for the excavator.

The hydraulic coupling characteristics, in addition to slippage at lowspeeds, are of any selected sort, and the coupling may have turbine ortorque multiplying characteristics. The illustration, such as Fig. 5, isdiagrammatic but discloses a type in which there is very little torquemultiplication but in which the centrifugal coupling is extremelyeffective. If no material torque multiplication is provided by thehydraulic couplingwe provide other means for changing the torque ratios.In the present instance, therefore, where the hydraulic coupling itselfhas very little torque changing characteristic, we provide theeight-speed transmission or some equivalent :gear-change mechanism whichis preferably partly automatic and partly under the control of thevehicle operator.

The particular ratio of the front transmission in the casing which iseffective at any one time is controlled by a valve shaft 34| rotatableby Van operators control levei` 342 or by an operating rod 343 regulatedby a speed-responsive governor 344 actuated by the frontground-eng'aging wheels I3. Thus the position of the shaft 34| isresponsive to the speed of the front groundof the front wheels I3, themore the shaft 34|l is rotated from its zero position. But it may berestrained in any selected position by the vehicle operator holding thelever 342, either by hand or with a latching structure (not shown) Ifthe lever 342 is held, the corresponding transmission remains intheselected ratio, but if the lever 342 is free then the particular ratiodepends upon the iront-wheel speed. Under governor control, however, thelever does not go into zero position, but at lowest wheel speed, orstopped, the lever occupies first speed position. Manual positioning ofthe lever in zero position, or neutral, is entirely possible.

In a quite similar fashion, the control rod 219 from the governor 218which is responsive to the speed of the rear ground-engaging wheels l2,extends to and is eifective upon the valve control shaft 346 for therear transmission. A manual controller 341 is in all respects comparableto the controller 342 and is located in juxtaposition therewith so thatthe two controllers 342 and 341 can be simultaneously actuated by theoperator, or can be simultaneouly latehed in position, or can beindividually located so that under rather unusual operating conditionsthe ratio of power transmission between the front engine and the frontwheels is diierent from the ratio of power transmission between the rearengine and the rear wheels. Normally, however, both engines are free totransmit power through the same or approximately the same ratio underautomatic wheel-speed responsive control.

Since the servo mechanism for translating the position of the shaft 34|into gear positions in the iront transmission is substantially the sameas the servo mechanism for translating the position of the controllingshaft 346 into corresponding gear positions in the rear transmission, adescription of but one of them applies to both. For example, air fromthe main 323 is conducted through supply pipes 35|, 352 and 353 to eachof three valves 354, 355 and 356 having substantally the same rotors`but having somewhat different valve casings. The valve 354 is providedwith but two ports, one port 351 being connected by a conduit 358 to oneend of an actuating chamber 359 comparable to the chamber 324 butconnected to the shifting fork I |3, for example. The piston in thechamber 359 is ordinarily in a neutral position, but when air is appliedto one end of the chamber it is shifted into one extreme position, andthat is what occurs when the valve 354 is rst rotated out of its zeroposition. The valve 354 likewise has a port 36| connected by a duct 362with the opposite end of the chamber 359.

The Valve 355 is provided with alternating and spaced ports 363 and 364which are connected by ducts 366 and 361 joining in a pipe 368 to oneend of a control chamber 399. Interspersed ports 31| and 31.2 join in aduct 313 connected to the opposite end of the control chamber 369. Thepiston of this chamber is effective upon the shifting fork |22.

The valve 356 is provided with a series of alternate ports 38|, 382, 383and 384, each of which is joined by its individual pipe to a duct 386extending to one end of a controller 381 effective upon the shiftingfork I3|. The valve 356 intermediate each of the ports 38|, 382, 383 and384 is provided with a series of ports 388, 389, 39| and 392 each ofwhich is connected by its individual pipe to a duct 393 extending to theopposite end of the controller 381.

Since the ratio-changing transmission has eight speeds, the controlshaft 34| has nine positions. The initial or zero position. isillustrated in Fig. 10 in which none of the valves is in a position tosupply air and all of the control cham- 5 bers 359, 36S and `381 are inneutral position with the various shifting forks ||3, |22 and I3|likewise in neutral position so that none of the gears is inpower-transmitting position. When, however, the shaft 34| is moved intoits Iirst Position, air pressure is transmitted through the port 351,through the port 363, and through the port 38| simultaneously, in orderto establish corresponding positions of the control chambers and therespective shifting forks. When the shaft 34| is moved to its secondposition, the ports 351 and 363 remain effective, but the port 388becomes effective. In the third position, while the port 351 is stilleiTective, the port 31| then becomes eiective and the port 382 iseffective, thereby duplicating the function of the port 38|. In fourthposition, the port 354 remains effective, the port 31| remainseffective, .but the port 389 is effective as previously the port 388 waseiective.

In fifth position, the port 36| becomes eiective,

the port 364 becomes effective in the fashion of the original port 363,while port 383 is effective.

In sixth position, port 36| is eiective, port 364 remains effective, butport 39| is effective. In

seventh position, port 36| is eiective, but port 312 then becomeseffective, while port 384 is connected. In eighth position, port 36| iseffective,

port 312 remains effective, while port 392 is effective.

In this fashion, the shifting fork ||3 remains in one extreme positionfor the first four speeds and then occupies a second extreme positionfor the second four speeds. The shifting fork 22 occupies one extremeposition for the first two speeds, occupies its other extreme positionfor the next two speeds, then the first extreme position for thesubsequent pair of speeds, and nally the second eXtreme position for theultimate pair of speeds. The shifting fork is alternately moved from oneextreme position to the other as the 46 range of speeds is traversed.Thus, in response to the position of the shaft 34|, the ratio of speedsbetween the front engine and the front ground-engaging wheels isautomatically or manually controlled. Since the controlling structure50,1501- the rear ratio-changing transmission is identical, the positionof the shaft 346 similarly controls the ratio betwen the rear engine andthe rear ground-engaging wheels, either automatically or manually.

Particularly under favorable or normal operating conditions, the speedtransmissions and hydraulic couplings provide an automatic connectionbetween the engines and the remaining driving structure, so that theoperator of our excavator need concern himself primarily with but thesteering, braking and throttle controls 251 and 25|. He, therefore, cangive plenty of attention to and has adequate time to operate the winchand hydraulic elevating structures of the earth-carrying portion of themachine. He is precluded from steering excessively at relatively highspeeds and is given the assistance of maximum drive and traction byvirtue of the locking differentials under most conditions. Under eX-treme conditions, however, the manual controls are available forproducing individual driving eiects, so that the full capabilities ofthe excavator can be obtained.

Under extreme operating conditions, or in certainl environments, it isadvisable to have an 17 auxiliary power structure, and we have,therefore, illustrated in Fig. 8 a device which is substantially thesame as previously described in all respects except that the main framestructure 40| is not articulated between its ends and is` not providedwith any earth handling structure .but rather extends simply as a frameto a rigid the ground, especially during cutting or excavat` ing, inaccordance with the load as represented by the speed of advance ofthevehicle. is, under conditions Where very hard going is encountered, thegoverned engines furnish maximum power but this may be insufficient tomaintain the speed of the vehicle and slower progress is made. Undersuch circumstances, it -is often advantageous to reducethe depth ofcutting in order to maintain the rate of advance of the vehicle. This iseffectuated automatically, d although manual supervision is retained.

Conversely, if the going is particularly easy, the cutting depth can beincreased without reducing the speed of advance of the vehicle, andunder those circumstances we provide a mechanism which automaticallywill increase the depth of cut so as to ensure that under allcircumstances the vehicle is making the best use of the maximum poweravailable from the power source. Most of the time the manual supervisioncan be omitted and the automatic mechanism relied upon, but there areoften unusual circumstances which can best bemet -by manually controlledmeans if, l A, C

Since this arrangementcan be applied to or That means, we preferablyprovide a second control valve 42| `arranged generally in parallel withthe valve 292. The construction of the valve 42| is like that of thevalve 292 and hence it receives uid under pressure from the duct 212through a branch duct 422 and is similarly connected to the dischargepipe 216 by a branch discharge pipe A423. In a comparable fashion thevalve 42| is connected to raise the main bowl I4 by supplying fluid tothe duct 4I3 through a branch duct 424, while the valve is connected tolower omitted from; the mechanism without substantially altering theremaining portions thereof, it is shown in a separate diagram in Fig.11, it being understood that this structure preferably is added to thestructure as diagrammatically illustrated` in Fig. 10. As illustrated inFig. 11, the main bowl I4 is movable vertically with respect to the mainframe I6, in order to move the cutting edge with respect to the ground,and this motion preferably efectuated by the cylinder and p1stonarrangement I8 which is connectedto the main bowl I4 by a piston rod 4II and which is hydraulically operated. i

The hydraulic liquid s obtained from the storage tank 268 from which itis conducted through the pipe 261 to the force pump 88 and is dischargedtherefrom under pressure through conduit 269 past the by-pass valve 21|and into the controlling valve 292 through the pipe 212. From the valve292, which is operated by the hand controller 29|, discharge either isthrough a pipe 4|2 into a duct 413 leading to the bottom of the cylinderI8 and which when connected is effective to lift the piston rod 4|I andcorrespondingly to raise the main bowl I4, or, in the alternative, isthrough a duct 4|6 into a pipe 4I1 leading to the top of thercylinder I8and effective to depress the main bowl I4 with respect to the ground.Thus, by operating the hand control 29|, as previously described, theoperator may, by hydraulic power, raise and lower Vthe main bowl I4 notonly with respect to the mainframe I6 but also with respect to theground. i

In order to provide an automatically effective the main bowl I4'bysupplyingfluid to the line 411 through a branch line 426. The controlvalve 42| is not provided with any manual lever but is operated by powersince its operating lever 421 is connected to a movable cylinder 428within which a piston 429 is stationarily established by a piston rod43| fastened to a fixed support 432. The cylinder 428 is centralizedwith respect to the piston 429 by interior springs 433 and 434.

Movement of the cylinder 42B is preferably in response to the speed of aground-engaging wheel, such as one of the rear wheels I2, through themedium of a servo or power'multiplying mechanism. Rotation of theground-engaging wheel I2 is normally effective through multiplyinggearing 436 to drive a sensitive governor 431 at a relatively highspeed. The multiplying mechanism 436 is desirable since duringexcavation the speed of advance of the vehicle is usually relativelyYslow and it is advisable, consequently, to make the governor highlyresponsive during low-speed operation. The governor 431 is connectedthrough linkage 438 to a slide valve 439 governing the supply toandexhaust from the cylinder 438 of a pressure fluid, such as air. Thisair is supplied from the source throughthe duct 302 under the control ofa valve 44| ywhich communicates with the movable valve 439 through a.flexible duct-'442.

'Theoperation of the mechanism is such that,

as the vehicle wheel speed I2 increases, the gov.

ernor 431 correspondingly changes its position and moves the valve 439correspondingly. This movement displacesthe valves 439 toward the right,as seen in Fig. 1l, uncovering the cylinder 428 to the left of thepiston 429 to the atmosphere through a port 443 and simultaneouslyuncovering a port 444 in the right-hand side of the chamber 428 to thesupply of pressure air through the valve 439. This produces acorresponding translation of the cylinder V428 in exact proportion tothe movement of the valve439 responsiveto the governor, and the cylindermovement rotates, through the lever 421, the valve 42| so thatcommunication is established between the supply duct 422 and thelowering duct 426, while liud discharge also occurs from the other endof `the cylinder 428, thereupon causing the main bowl I4 to lower withrespect to the ground or to cause the cutting edge to engage the groundmore deeply. 'Ihis normally increases the load upon the vehicle andslows its advance to the optimum value.

When the speed of the vehicle is VVless than the optimum value and thewheel I2 drops below that speed, the governor 431/is correspondinglyaffected, and the valve 439 is translated toward the leftin Fig. 1l,thereby exposing the port 444 to atmosphere and connecting the port 443to the supply of air, thereby displacing the movable cylinder 428 towardthe left in the ligure, rotating the valve 42| in a clockwise direction,andiconnecting the supply duct 422 to the raisine lduct 424. Thus, `whenthe speed or the 19 vehicle drops below the optimum value the main bowlI4 is raised and the cutting edge is lifted with respect to the ground,thereby normally decreasing the load upon the engine and permitting thevehicle speed to be restored.

In accordance with the operation of this mechanism, the position of themain bowl 'is maintained at a value which will afford substantially aconstant speed of advance of the vehicle with-A out operatorssupervision and automatically. Y

But since such automatic regulation is of value chiey during excavation,and since the sensitive governor 437 may be damaged vby over-speedingwhen the vehicle is transporting a load or dumping a load, we providelmeans for disabling the automatic structure except during excavation.The piston rod 4|4 carries a collar `45| which moves with such rodbetween the maximum excavating position indicated by the dotted lines452 in Fig. 1l, between the maximum raised position indicated by thedotted lines 453 in that ligure, and the intermediate position shown bythe solid lines in Fig. 11 wherein the cutting edge is supposedlysubstantially ush with the surface of the ground.

As the collar 45| rises from the central position illustrated, whereinthe cutting edge is substantially even with the surface of the ground,it engages and lifts with it a lever 454 against the urgency of a spring456, and the motion of the lever is transmitted through linkage 451 todisengage a driving clutch 458 interposed in the drive line between therear Awheels I2 and the multiplication gearing 436. Thus, as the mainbowl I4 rises above its ground-level position, the

clutch 458 is disengaged and no motion is transmitted to the governor431. Under these circumstances, in the event no manual control isexercised, the operation of the governor is such as tor produce anextreme displacement of the valve 439 so that the valve 42| is rotatedto bring the main bowl 'I4 toits maximum elevated position for carriage.Whenever the governor is 'brought to its declutched or stationaryposition, as, for example, when the cutting edge strikes an obstruction,or when the load is so great as to slow the vehicle materially, asimilar operation of the valve 439 promptly brings the bowl to highestcarrying position.

When the main bowl I4 is lowered to and below the central position, andas the collar 45| descends, the spring 456 is effective upon the lever454 and the linkage 451 to engage the clutch 453 and tobring thegovernor 431 up to speed. Below the central position, therefore, theoperation is automatically controlled.

Manual control by the lever 29| at all times supersedes automaticcontrol when the operator so desires, and to effectuate that conditionthe lever 29| is provided with an extension 46| adapted to cam against alever 462 bearing upon the end of a valve stem 463 joined to the valve464. The valve is ordinarily pressed by a spring 466 into an uppermostposition against the lever '462 which in turn presses against theextension 46|. When the hand control lever 29| is in its central orneutral position, so that the valve 292 is ineiective to produce anymovement of the main bowl I4, the lever 462 is depressed, as is the stem463, against the urgency of the spring 466, so that the valve 464permits free communication of air from the duct 302 to the valve 439 andthe servo cylinder 428. Thus, when the hand controller 29| is in acentral or inactive position, the automatic .mechanism can operatewithout restriction. But when the hand controller 29| is moved in eitherdirection `from its neutral position, -the immediate effect is for theextension 46| to permit the lever 462 to rise with the stem 463 underthe urgency of the spring 465. Simultaneously, the valve 464 rises,thereby cutting oil Vcommunication from the source of air 392 to theservo valve 439 and connecting such valve to atmosphere through a drainduct v46T'. Since, therefore, -despite t-he position momentarily of thevalve 439, the cylinder 423 is connected -on both sides of the piston429 to atmosphere, the centralizing springs 433 and 434 are effectiveinstantly to restore the automatic valve 42| to a central, neutral orineffective position, andthe manual control lever 29| is the sole meansof producing motion of the main bowl I4. As soon, however, as manualcontrol of the lever 29| is relinquished, or the lever is restored toits central neutral position, the valve 464 is again positioned so thatthe valve 439 is supplied with air and vthe automatic 4servo mechanismis restored to eiiectiveness.

By the provision -of this mechanism, therefore, it is possibleto havethe lmaximum -utilization of the engine power, as measured by the speed-of advance ofthe vehicle, effective to control the depth of cut or, ingeneral, the position of the main bowl 14, although manual supervisionis retained and the automatic control is made ineffective except for -a`portion of the range -of movement of the main 4bowl with respect to theground.

We claim:

l. A vehicle` comprising: a frame; yrear .wheels for Ysupporting saidframe; a first means connected to drive said rear wheels; front wheelsfor supporting and steering said frame; a second means connected todrive said front wheels; means for steering said front wheels; and meansresponsive to the steering Aof said -front wheels for altering thedriving connection of said second means to 'said front wheels.

2. A vehicle comprising: 'a frame; rear wheels 45 for lsupporting said:fra-me; a rst means connected to drive'said rear wheels; front wheelsfor supporting andV lsteering sai-d if-rame; a second means `connectedto drive -said front wheels; means -for steering Asaid front wheels;-and means responsive to the Asteering of said -front wheels for alteringthe drivingl connection of Vsaid rst means tosaid rea-r wheels.

3. A vehicle comprising: a frame; rear wheels for supporting said frame;a iirst lmeans Vconnected to drive -said rear wheels; front wheels forsupporting Aand steering said frame; a second means connected -to drivevsaid front wheels; means for s-teerin-g said -front wheels; and meansresponsive to the steerin-g :of said iront wheels for altering -the4driving connection Abetween said second means and said yiront wheelsand between said` rst-means and said rear wheels.

4. A vehicle comprising: a frame; rear Wheels for supporting said frame;Ya first means .carried y(55 bysaid frame and arranged to drive saidrear wheels; dirigible front wheels for 'supporting said frame; a secondmeans arranged to drive said front wheels; means for steering saiddirigible wheels; and means responsive to the steering of said frontwheels a predetermined amount for alter-ing the driving connectionbetween said second means and said front wheels.

5. A vehicle comprising: -a main frame and main Ibody structure; rearwheels for supporting said structure; a iirst means` connected to drive21 said rear wheels; front wheels for supporting and steering saidstructure; a second means connected to drive said front wheels; meansfor steering said front wheels; and means responsive to the steering ofsaid front wheels a predetermined amount for altering the drivingconnection of said second means to said front wheels and responsive tothe steering of said front Iwheels a different amount for altering thedriving connection of said rst means to said rear wheels.

6. A vehicle comprising: a frame; rear wheels for supporting said frame;a rst means for driving said rear wheels;` a rear differential forvariably dividing power from said iirst means between said rear wheels;a rear diflerentiallock for disabling said rear diierential; frontwheels for supporting said frame; a second means for driving said frontwheels; a front differential for variably dividing power from saidsecond means between said front wheels; a front differential lock fordisabling said front differential; and common control means foroperating said front and rear differential locks.

7. A vehicle"comprising: a frame; rear'wheels for supporting said frame;a iirst means for driving said wheels; a rear ratio-changingtransmission for transmitting power from said first means to said rearwheelsmeans responsive to the speed of said rear wheels for controllingsaid transmission; a rear reversing mechanism interposed between saidfirst means and said transmission; front wheels for supporting saidframe; a second means for driving said front wheels; a frontratiochanging transmission for transmitting power from said second meansto said front Wheels; a front reversing mechanism interposed betweensaid second means and said front transmission; means responsive to thespeed of said front wheels for controlling said front transmission; andcommon control means for operating said rear reversing mechanism andsaid front reversin mechanism.

8. A vehicle comprising: a frame; rear wheels for supporting said frame;a rst means for driving said rear wheels; a rear differential forvariably dividing power from said first means between 22 said rearwheels; a rear differential lock for dis abling said rear differential;front Wheels for supporting said frame; a second means for driving saidfront wheels; a front differential for variably dividing power from saidsecond means between said front wheels; a front differential lock fordisabling said front differential; means for steering said front wheels;and means responsive to said steering means for operating said `irontand rear differential locks and for controlling said first means. n

9. A vehicle comprising: a frame; rear Wheels for supporting said frame;front wheels for supporting and steering said frame; driving meansconnected to drive said front wheels; means for steering said frontwheels; and means responsive to the steering of said front wheels foraltering the connection of said driving means to said front wheels.

10. A vehicle comprising: a frame; rear wheels for supporting saidframe; front wheels for supporting and steering said frame; drivingmeans connected to drive said rear wheels; means for steering said frontwheels; and means responsive to the steering of said front wheels foraltering the connection of said driving means to said rear wheels.

11. A vehicle comprising a frame; rear wheels for supporting saidframe;` dirigible front wheels for supporting said frame; means 'forsteering said front wheels into a position with the planes of saidwheels approximately transverse of said vehicle; means for driving allof said wheels; and means for altering the driving of said rear wheelsin response to said steering means.

12. A vehicle comprising a frame; rear wheels for supporting said frame;dirigible front wheels for supporting said frame; means for steeringsaid front wheels into a, position with the planes of said wheelsapproximately transverse of said vehicle; means for driving al1 of saidwheels, and means for substantially releasing said rear wheels from saiddriving means upon steering of said front wheels approximately into saidposition.

R. E. CHOATE'. ELLSWORTH W. AUSTIN.

